Assistive devices such as augmentative and alternative communication (AAC) systems are used by people with communication and motor disabilities, such as amyotrophic lateral sclerosis (ALS, commonly known as Lou Gehrig?s disease), to communicate and interact with their environment. There are various commercially available AAC devices that are controlled by access methods such as touch, switch, head tracking and eye gaze; however, these access methods become difficult or impossible to use when sustained muscle control is more challenging or voluntary motor control is lost. There are brain-computer interface (BCI) communication systems, such as the P300 speller, that use sensory stimulation to elicit and then detect sensory neural responses in electroencephalography (EEG) data, and these communication aids do not require any motor control on the part of the affected individual. However, the accuracies and spelling speeds of stimulus-driven BCIs are suboptimal due to the inherent limitations associated with relying on sensory stimulation, which generates highly variable neural responses, as well as the necessity of processing inherently noisy EEG data to extract the relevant neural information that is needed to control the BCI. Current BCI communication rates can potentially be improved with closed-loop optimisation techniques that exploit information from the user?s responses to previous stimuli to optimally tune the BCI system?s parameters to achieve the desired goal of maximising system performance under conditions of uncertainty. A closed-loop strategy can be used to select stimuli that are maximally informative of the user?s intent given the neural responses that are being measured, and I hypothesise that this data-adaptive approach to stimulus selection will minimise BCI decision errors and achieve better device control. Conventional BCIs use open-loop stimulus control methods as the stimulus presentation schedule is typically set in advance or occurs randomly, and there has been limited development of closed-loop stimulus paradigms in BCIs. The goal of the research that I propose is to investigate the feasibility of a novel closed-loop stimulus selection algorithm that will optimise the BCI stimulus presentation schedule in real-time based on the measured EEG data and the BCI system?s belief about the user?s intent, with proof-of-concept demonstrated in the P300 BCI speller.
Specific Aim 1 will initially develop and test the novel algorithm in a non-disabled cohort to leverage the time efficiency and practicality of non-disabled participant studies to evaluate the real-time feasibility and potential utility of the closed-loop stimulus selection algorithm.
Specific Aim 2 will test the closed-loop stimulus selection algorithm in individuals with ALS to assess the performance of the algorithm in a clinically relevant cohort. The successful development and testing of the proposed closed-loop stimulus selection algorithm in a challenging system such as the P300 BCI speller has the potential to instigate a paradigm shift towards closed-loop methods for BCI control and other applications where optimising system parameters in real-time to improve overall system performance could be of benefit.

Public Health Relevance

People with significant motor disabilities often require assistive devices such as augmentative and alternative communication (AAC) systems to communicate and interact with their environment. Brain-computer interfaces (BCIs) can provide access to AAC systems and other devices for individuals with little to no voluntary muscle control in order to facilitate their communication with the outside world; however current BCI communication accuracies and speeds are suboptimal. The goal of this research effort is to develop and test the use of closed-loop optimisation techniques in BCI system design, where information from previous user responses and actions by the system is considered during the selection of the next action of the system. These closed loop techniques will be used to optimise BCI stimulus presentation parameters during real-time use to improve BCI communication efficiency, and demonstrated success of the proposed closed-loop stimulus optimisation method in real-time BCI use has the potential to accelerate the translation of BCI systems into viable AAC devices.

National Institute of Health (NIH)
National Institute on Deafness and Other Communication Disorders (NIDCD)
Exploratory/Developmental Grants (R21)
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Communication Disorders Review Committee (CDRC)
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Shekim, Lana O
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Duke University
Engineering (All Types)
Biomed Engr/Col Engr/Engr Sta
United States
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